Twitter is adding Black Entertainment Television CEO Debra Lee to its board, part of a broader promise by one of Silicon Valley's less diverse companies to become more inclusive.

Lee rose to the top of BET Networks in 2006 after 20 years with the cable channel, one of the oldest targeting African-Americans. BET is part of Viacom.

"Debra's addition strengthens our board immensely," Twitter Executive Chairman Omid Kordestani said in a statement Monday. "She's a highly respected leader in the media industry with decades of experience, and has a clear passion for Twitter as a service and a company."

The San Francisco-based social network also announced on Monday that board member Marjorie Scardino had been appointed lead independent director.

The appointments comes as Twitter and other tech companies continue taking heat for their lack of diversity. Twitter, in particular, is male-dominated, with more than 70 percent of its leadership male and white. That's less diverse than LinkedIn, Apple, eBay and Amazon.com.

Longtime civil rights leader Rev. Jesse Jackson, who has been urging tech companies to diversify, said in an interview Monday he's known Lee for decades and that her media experience definitely brings "added value" to Twitter.

"Debra Lee is extremely qualified, she has integrity and deep community roots," Jackson said. "This is a giant step for Twitter, but we all know there's more work to be done."

The issue of diversity has bubbled over into the public at Twitter. Last fall, Leslie Miley, an African-American engineer who held a leadership role at Twitter before departing, had publicly questioned the social network's commitment to diversity. Miley is now a director of engineering at San Francisco messaging startup Slack.

Just last month, during Twitter's earnings call, CEO Jack Dorsey, reaffirmed a promise to boost diversity across the company, including at the board level.

They also come a month after the social network announced Pepsi Chief Financial Officer Hugh Johnston and Martha Lane Fox, a co-founder of the travel website Lastminute.com, would be joining the eight-person board.